Question

20 - 8 x = -19-21 ×?

Answer 1

20-8x=-19-21x
-8x+21x=-19-20
13x=-39
x=-39/13
x=-3
Resposta:  -3  

Answer 2

Vamos Lá:

$20-8x = -19-21x$
$-8x+21x = -20-19$
$13x = -39$
$x = \dfrac{-39}{13}$

$\boxed{x = -3}$

Bons Estudos!!!